Bottom Line:
In this context, the evaluation of the possible effects exerted by palladium nanoparticles (Pd-NPs) on the immune system is essential to comprehensively assess palladium immunotoxic potential.The highest concentration of Pd-NPs (12 μg/kg) induced a significant increase of IL-1α, IL-4, IL-6, IL-10, IL-12, GM-CSF and INF-γ compared to controls.Our findings did not show an imbalance between cytokines produced by CD4+ T helper (Th) cells 1 and 2, thus suggesting a generalized stimulation of the immune system with a simultaneous activation and polarization of the naïve T cells towards Th1 and Th2 phenotype.

Background: Information currently available on the impact of palladium on the immune system mainly derives from studies assessing the biological effects of palladium salts. However, in the last years, there has been a notable increase in occupational and environmental levels of fine and ultrafine palladium particles released from automobile catalytic converters, which may play a role in palladium sensitization. In this context, the evaluation of the possible effects exerted by palladium nanoparticles (Pd-NPs) on the immune system is essential to comprehensively assess palladium immunotoxic potential.

Aim: Therefore, the aim of this study was to investigate the effects of Pd-NPs on the immune system of female Wistar rats exposed to this xenobiotic for 14 days, by assessing possible quantitative changes in a number of cytokines: IL-1α, IL-2, IL-4, IL-6, IL-10, IL-12, GM-CSF, INF-γ and TNF-α.

Methods: Twenty rats were randomly divided into four exposure groups and one of control. Animals were given a single tail vein injection of vehicle (control group) and different concentrations of Pd-NPs (0.012, 0.12, 1.2 and 12 μg/kg). A multiplex biometric enzyme linked immunosorbent assay was used to evaluate cytokine serum levels.

Results: The mean serum concentrations of all cytokines decreased after the administration of 0.012 μg/kg of Pd-NPs, whereas exceeded the control levels at higher exposure doses. The highest concentration of Pd-NPs (12 μg/kg) induced a significant increase of IL-1α, IL-4, IL-6, IL-10, IL-12, GM-CSF and INF-γ compared to controls.

Discussion and conclusions: These results demonstrated that Pd-NP exposure can affect the immune response of rats inducing a stimulatory action that becomes significant at the highest administered dose. Our findings did not show an imbalance between cytokines produced by CD4+ T helper (Th) cells 1 and 2, thus suggesting a generalized stimulation of the immune system with a simultaneous activation and polarization of the naïve T cells towards Th1 and Th2 phenotype.

Mentions:
The Pd-NPs hydrosol obtained was characterized by continuum source—graphite furnace atomic absorption spectrometry (CS-GFAAS; contrAA 600, Analytik Jena, Jena, Germany) and transmission electron microscopy (TEM; Zeiss EM 10, Carl Zeiss Microscopy GmbH, Jena, Germany) operating at 80 kV. The Pd concentration of the stock hydrosol was determined in a 100-fold dilution of the stock hydrosol in ultra pure water by means of CS-GFAAS using the spectral line at 244.791 nm. Calibration was performed in a concentration ranging from 20 to 80 μg Pd/L by applying adequate dilutions of a Pd stock standard solution (1000 mg/L, Pd(NO3)2 in 0.5 mol/L HNO3, traceable to Standard Reference Materials from the National Institute of Standards and Technology, Merck, Darmstadt, Germany) in 0.5 mol/L HNO3. This resulted in a linear calibration function with a correlation coefficient of 0.986. The stock hydrosol Pd concentration was found to be 4.71 ± 0.05 mg/L. The measurement of 500 individual particles depicted by TEM images using ImageJ software (National Institutes of Health, Bethesda, MD) revealed the size distribution of the particles to be 10 ± 6 nm (Fig 1). The hydrosol served as a stock solution for all experiments and is stable for at least 2 weeks when stored in refrigerators at 4°C. Before use, the stored Pd-NP hydrosol was homogenized by shaking vigorously. Finally, aliquots of the stock solution were diluted in ultrapure water to obtain the final concentrations used in the experiments.

Mentions:
The Pd-NPs hydrosol obtained was characterized by continuum source—graphite furnace atomic absorption spectrometry (CS-GFAAS; contrAA 600, Analytik Jena, Jena, Germany) and transmission electron microscopy (TEM; Zeiss EM 10, Carl Zeiss Microscopy GmbH, Jena, Germany) operating at 80 kV. The Pd concentration of the stock hydrosol was determined in a 100-fold dilution of the stock hydrosol in ultra pure water by means of CS-GFAAS using the spectral line at 244.791 nm. Calibration was performed in a concentration ranging from 20 to 80 μg Pd/L by applying adequate dilutions of a Pd stock standard solution (1000 mg/L, Pd(NO3)2 in 0.5 mol/L HNO3, traceable to Standard Reference Materials from the National Institute of Standards and Technology, Merck, Darmstadt, Germany) in 0.5 mol/L HNO3. This resulted in a linear calibration function with a correlation coefficient of 0.986. The stock hydrosol Pd concentration was found to be 4.71 ± 0.05 mg/L. The measurement of 500 individual particles depicted by TEM images using ImageJ software (National Institutes of Health, Bethesda, MD) revealed the size distribution of the particles to be 10 ± 6 nm (Fig 1). The hydrosol served as a stock solution for all experiments and is stable for at least 2 weeks when stored in refrigerators at 4°C. Before use, the stored Pd-NP hydrosol was homogenized by shaking vigorously. Finally, aliquots of the stock solution were diluted in ultrapure water to obtain the final concentrations used in the experiments.

Bottom Line:
In this context, the evaluation of the possible effects exerted by palladium nanoparticles (Pd-NPs) on the immune system is essential to comprehensively assess palladium immunotoxic potential.The highest concentration of Pd-NPs (12 μg/kg) induced a significant increase of IL-1α, IL-4, IL-6, IL-10, IL-12, GM-CSF and INF-γ compared to controls.Our findings did not show an imbalance between cytokines produced by CD4+ T helper (Th) cells 1 and 2, thus suggesting a generalized stimulation of the immune system with a simultaneous activation and polarization of the naïve T cells towards Th1 and Th2 phenotype.

Background: Information currently available on the impact of palladium on the immune system mainly derives from studies assessing the biological effects of palladium salts. However, in the last years, there has been a notable increase in occupational and environmental levels of fine and ultrafine palladium particles released from automobile catalytic converters, which may play a role in palladium sensitization. In this context, the evaluation of the possible effects exerted by palladium nanoparticles (Pd-NPs) on the immune system is essential to comprehensively assess palladium immunotoxic potential.

Aim: Therefore, the aim of this study was to investigate the effects of Pd-NPs on the immune system of female Wistar rats exposed to this xenobiotic for 14 days, by assessing possible quantitative changes in a number of cytokines: IL-1α, IL-2, IL-4, IL-6, IL-10, IL-12, GM-CSF, INF-γ and TNF-α.

Methods: Twenty rats were randomly divided into four exposure groups and one of control. Animals were given a single tail vein injection of vehicle (control group) and different concentrations of Pd-NPs (0.012, 0.12, 1.2 and 12 μg/kg). A multiplex biometric enzyme linked immunosorbent assay was used to evaluate cytokine serum levels.

Results: The mean serum concentrations of all cytokines decreased after the administration of 0.012 μg/kg of Pd-NPs, whereas exceeded the control levels at higher exposure doses. The highest concentration of Pd-NPs (12 μg/kg) induced a significant increase of IL-1α, IL-4, IL-6, IL-10, IL-12, GM-CSF and INF-γ compared to controls.

Discussion and conclusions: These results demonstrated that Pd-NP exposure can affect the immune response of rats inducing a stimulatory action that becomes significant at the highest administered dose. Our findings did not show an imbalance between cytokines produced by CD4+ T helper (Th) cells 1 and 2, thus suggesting a generalized stimulation of the immune system with a simultaneous activation and polarization of the naïve T cells towards Th1 and Th2 phenotype.